1. Field of the Invention
The present invention relates to a magnetic recording and reproducing apparatus with a built-in head cleaning device. More specifically, in a magnetic recording and reproducing apparatus using a tape cassette having a write-protect function for inhibiting data from being re-written, when a magnetic head is cleaned, a head cleaning is implemented based on attribute information which is not related to original data in record information and this attribute information can be re-written regardless of a write-protect mode, whereby a correct head cleaning can be executed only by the attribute information.
2. Description of the Related Art
In a tape cassette (tape streamer) used in order to save computer data, most of magnetic recording and reproducing apparatus include magnetic head cleaning device for enabling data to be correctly recorded and reproduced (written and read out).
A head cleaning should be executed at a proper timing. If the head cleaning is executed too frequently, then the head will be worn easily, and a life span of head will be shortened. If the number of the head cleaning is reduced too much, then the head will be smudged. There is then the risk that data cannot be recorded and reproduced correctly. When a head cleaning is not executed properly, it is considered that this will exert an adverse effect upon a life span of a plunger which operates a cleaning roller for cleaning a magnetic head.
Therefore, a head cleaning processing should be executed at a proper timing. It is customary that a magnetic head is smudged depending upon a condition of a cassette tape used. The reason is that a tape itself is progressively damaged as the number in which the tape is loaded onto the apparatus increases, thereby resulting in the magnetic head being smudged increasingly.
Similarly, the number in which data is overwritten and the frequency in which an error occurs (error log) are considered as factors for determining whether or not a head is smudged. For example, when a frequency at which an error occurs is large, it is considered that a head is smudged accordingly.
Therefore, a head cleaning timing should be determined considering a condition under which a tape is in use. As a typical example of factors for determining the condition under which the tape is in use, there are enumerated the number of the tape loading, the number of the overwriting and the number of errors (these factors will hereinafter be collectively referred to as system log).
Contents of system log are generally saved together with original data in the tape as attribute data (attribute information). The system log can be recorded on a system log area provided in a data format which records data. Thus, when a tape cassette is loaded onto an apparatus, it is possible to calculate a frequency at which a tape is in use with reference to the system log area.
There are tape cassettes of the structure incorporating an auxiliary memory means, for example, a one with a built-in memory means using a non-volatile semiconductor memory (memory-in-cassette (MIC): details thereof will be described later on). In case of such tape cassette incorporating the memory, contents of system log can be recorded not in a tape but in this memory.
There are tape cassettes having a so-called write-protect function which inhibits recorded data from being erased. When the tape cassette is placed in the write-protect state, data can be read out but data cannot be re-written (re-recorded). Attribute information also cannot be re-recorded. This is also true in the MIC cassette.
Considering the way the cassette is used, when the tape cassette is in use, the recording of data is not always executed.
It is frequently observed that data is only read out and only the read-out data is used. This is also true in the tape cassette of which the write-protect mode is operated.
When the tape cassette, which is placed in the write-protect mode, is in use, even if the number of the loading increases, the contents of the system log are the same and not changed. The log data are those obtained before the tape cassette is placed in the write-protect mode. However, it is considered that, when the tape cassette is loaded on the magnetic recording and reproducing apparatus and data is read out from the tape, the tape is smudged frequently. Therefore, the number of the loading presented when the tape cassette is placed in the write-protect mode should be used as head cleaning determining information.
In the case of the tape which is set to the write-protect mode, even though the head cleaning should be executed at the stage the write-protect is released, it is frequently observed that the head cleaning time has already been missed at that time.